Briggs & Stratton 35 Classic engine, blue smoke + oil residue out of exhaust + Petrol in oil

I had one similar come in with same problem fuel in oil. The carb was putting out too much fuel and was being sucked back through the crank case breather that connects to the carburetor. I replaced the carburetor and fixed it. Though the carburetor has no needle valve it does have neoprene gasket that is used to pump fuel. One of these has cracked and is allowing the fuel to flow back into the crankcase.
The other posters are assuming the tank is above the carburetor which the carb sets on top of the fuel tank and fuel is sucked up through the tube by the suction created in the crankcase on the neoprene gasket that is a pump. If this neoprene gasket has a small hole in it will put fuel into the oil.
 
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The float in the carb may need adjusting. If the float in the car
LochlanR said:
Just bought and serviced a 35 Classic engine on a push mower, Started it and there was alot of blue smoke, although I did have to replace two back wheels so I had it on its side for about 20 mins. When i got it the oil looked to be over filled quite a bit so made sure to change it to the right amount before starting it. After starting, it took ages to burn off the oil until it eventually cleared. Used it to cut the grass and left it for a couple days. Just went to start it now and it shot out a cloud of blue smoke, its been kept upright and not on its side, checked the oil, its gone very dark gray after one use and smells a bit like petrol has mades its way into it.

What could be the issue? I assume it to be the piston rings or something relating to that.
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b does not shut off the fuel when the bowl is full it will enter the cylinder and drain down past the rings into the crankcase. Itcould also be your needle valve and seat, which are the parts that close the fuel port to the bowl. I hope this helps
 
Rivets said:
Born to Mow, do you realize that he has a tank mounted pulsajet carb. There is NO fuel line. Loch, the only way that this can happen twice is that you have oil which entered your tank somehow when you tipped the mower with the carb down. Run it a couple of times with fresh petrol and it should clear up. If it doesn’t post back and we’ll look for other solutions.
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When tipping a push mower on it's side, if you go through this process first, no oil will enter the cylinder. First take ith pull rope in your hand and pull on it slowly, you will feel differences in resistance as you pull on the rope. When you get to the point of most resistance, the engine will be at top dead center and both intake and exhaust valves will be closed. Stop pulling on the rope at this time on your pull. With the engine at top dead center and both valves closed,no oil can enter your engine. At this time you can tip the mower on it's side and clean under your deck, take the blade off to sharpen, or whatever else you are about to do. I hope this helps you.
 
Besides some on here under the impression he has a tank over the carb, which is wrong, it's a tank mounted carb, you're ignoring the fact it appears he has fuel building up in his crankcase, which could be a bad pump diaphragm in the carb. That's why they are called pulsajets. It pulsates using the crankcase vacuum to pump fuel. If corrupted, fuel can leak by back through into the engine crankcase, causing an overfilling situation, and heavy smoke upon starting. Solution is a new diaphragm pump, or because the carbs are very common and affordable, a new carb is probably the best idea.
All of that said, you could also have bad rings, allowing unburnt fuel to pass by the rings into the crankcase. If you have the means, you may want to check the compression. It should be between 80 and 120 psi. Have a great day!
 
With this carb setup it's really hard to get gas back into the crankcase oil, i'm wondering if you might have a fuel cap that the vent is plugged over pressuring the tank forcing gas out and into crankcase, just my 2 cents.
 
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